Cancer Incidence Related Definitions and Associated Formulas
This link shows formulas used to calculate rates with examples.
Crude rate - The number of new cases or deaths during a specific time period
per 100,000 individuals. There is no consideration (adjustment) given to the age
Age-specific rate - The number of new cases diagnosed per 100,000 individuals
over a specific time period for a specific age group.
Age-adjusted rate - Cancer rates vary with age, and populations vary by their
age distributions. Age adjustment allows for comparison of rates between different
populations with different age structure. The "effect of age" is no longer present
upon age-adjustment. Age-adjusted rates are calculated using the age distribution
of the 2000 US standard population, and they are usually expressed per 100,000 population.
Mortality - The number of deaths occurring during a specific time period.
Diagnosis may have occurred prior to that specific time period.
Incidence - The number of new cases diagnosed during a specific time period
(i.e. one year).
Prevalence - A measure of the proportion of persons in a population with
a certain disease at a given time. The SCCCR does not collect prevalence.
Five-year survival - The percentage of people with a given cancer who are
expected to survive five years or longer with the disease.
95% Confidence Intervals r ± 61.981*(r/n)1/2
Where r = live birth rate, n = number of live births or population denominator,
When frequencies are less than 100 then 95% confidence intervals are calculated
using the formulas provided on pages 98-102 in the NCHS 2001 Birth Report a pdf document.
RATE CALCULATIONS WITH SMALL NUMBERS: There are variations in all statistics
that are the result of chance. This characteristic is of particular importance in
classifications with small numbers of events where small variations are proportionately
large in relation to the base figure. As an example, small changes in the number
of deaths or births in small population areas or in the number of deaths from uncommon
causes could result in large changes in these crude rates. For this reason, rates
for counties with small populations or other small bases should be used cautiously.
RaceInformation on race of the mother and father is reported on birth and
fetal death certificates, and the race of the decedent is reported on death certificates.
Fetal deaths are reported by race of mother. As of 1990, Live Births are reported
by race of mother instead of race of child. This change allows South Carolina's
birth data to be consistent with the National Center for Health Statistics and other
states throughout the United States. Race is reported as White, Black Other, and
Unknown. Other race group includes asian, pacific islander, and native americans.
Age - Age at diagnosis
With the exception of population data by race and population data for selected age
groups of teens, the 2000 Census data, provided by the Office of Research and Statistics
(South Carolina Budget and Control Board), were used to calculate the rates in this
report. Population data by race and for selected age groups were modified. Age Adjusted
rates use 18 age groups and the corresponding 18 standard weights from the 1970
and 2000 U.S. population.
POPULATION DATA BY RACE:The U.S. Census Bureau Population data contains data
for both "multiple race", and single race categories. This presents problems for
calculating vital statistical rates. The following methodology was developed jointly
by Office of Research and Statistics, South Carolina State Budget and Control Board
and the Division of Biostatistics and Health GIS, Public Health Statistics and Information
The populations of these two race categories were allocated to the standard single
race categories by age, gender and county. This allocation was based on the proportional
distribution of the population of the standard single race categories within each
of these age, gender, county groups.
POPULATION DATA FOR SELECTED AGE GROUPS:
For inter-census years, ORS provides estimated population data for South Carolina
by age for five-year age groups. It is assumed that the population within each of
these age categories is distributed uniformly through out the age interval. Based
on this assumption, the population for females 14-17, 15-17 and 18-19 years is derived,
consecutively, as follows - (20% of the female population 10-14 years plus 60% of
the female population 15-19 years), (60% of the female population 15-19), and (40%
of the female population 15-19).
RESIDENCE DATA: Data allocated to the place in South Carolina where the person
normally resided, regardless of where the event occurred.
Stage at diagnosis - The extent of disease spread from the organ of origin
at time of diagnosis. The SCCCR uses the SEER General Summary Staging System. This
system includes five stages: in situ, localized, regional, distant, and unstaged.
In situ and localized are classified as "early stage." Regional and distant are
considered "late stage." Cancers diagnosed as in situ are considered pre-invasive.
Localized, regional, and distant staged cancers are invasive.
In situ stage - Classification for pre-invasive malignancies, those that
do not invade the basement membrane.
Localized stage - Classification for invasive malignancies that are confined
to the organ of origin.
Regional stage - Classification for cancer spread by direct extension to
adjacent organs or tissues, and/or spread to lymph nodes considered regional to
the organ of origin, but no further spread has occurred
Distant stage - Classification of cancer spread beyond adjacent organs or
tissues, and/or metastasis to distant lymph nodes or tissues.
Unstaged - Classification resulting from insufficient information available
to determine stage of disease at diagnosis
Early stage - Grouping which includes in situ and localized stages of disease.
Late stage - Grouping which includes regional and distant stages of disease.
Cancer Grade - Grade is a 4-point scaling system determined by a pathologist
to describe the degree of differentiation of cancer cells. Differentiation describes
how abnormal the cells look under a microscope and probable rate of tumor growth
and spread. Well-differentiated, Grade 1 or low grade tissues often look the most
like normal cells; where as undifferentiated, Grade 4 or high grade tissues often
look the least like normal cells.
SOURCES OF INFORMATION
Centers for Disease Control (CDC) - Located in Atlanta, GA, the CDC is an
agency of the Department of Health and Human Services. The CDC serves as the national
focus for developing and applying disease prevention and control, environmental
health, and health promotion and education activities designed to improve the health
of people of the United States.
National Program of Cancer Registries (NPCR) - Funded by the CDC, the NPCR
is a population-based system of cancer registries established in 1992 by the Central
Cancer Registries Amendment Act (Public Law 102-515). When fully implemented, programs
funded by the NPCR will collect data on cancer for 96% of the US population.
Surveillance, Epidemiology and End Results (SEER) - Program of the National
Cancer Institute that collects and publishes cancer incidence and survival data
from 11 population-based cancer registries and three supplemental registries covering
approximately 14 percent of the United States population.
Cancer site - The body organ or system where cancer originates; the anatomical
site of origin.
Metastasis - Movement of disease from one organ or part to another not directly
Risk factor - Anything that increases a person's chances of getting a disease.
Examples include smoking, diet, and age.
Cancer cluster- A group of more cancer cases than normal in a small area,
like a neighborhood, or within a short time period. Cancer clusters are reported
when people learn that an unusual number of their friends, family, neighbors or
co-workers have cancer
COUNTIES BY REGIONS
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